Conventionally, pointer input devices such as keyboards, mice, trackballs, light pens and touch screens become essential peripheral input devices of information systems for allowing the users to input signals therevia. The above pointer input devices, however, have respective disadvantages and limitations. For example, the trackballs are not suitable to write onto upright-type large-sized screens. The light pens may only work with scan type monitors such as cathode ray tube (CRT) monitors, but not work with LCD screens, projectors or other display devices. A large-sized touch screen has problems of poor alignment and inconvenience for portability. As for the optical sensors used in the conventional optical pointer systems, image distortion such as barrel distortion or pincushion distortion is commonly encountered in the optical lens. Unfortunately, the effect of correcting the image distortion is often disappeared in the case of careless collision with the optical lens.
Nowadays, for most upright-type large-sized projection screens, a single keyboard and a mouse are used with the computer system to control the input pointer. As known, it is difficult to implement multi-input or opinion exchange by a single input device.
Therefore, there is a need of providing an input method of a pointer input system having the advantages of easy correction, excellent alignment and high resolution.